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### Gravity

Posted: **December 7th, 2018, 6:49 pm**

by **colin**

I caught the tail end of a Jim Al-Khalili program on Gravity last night where he said that stuff seems to fall in the direction in which time flows faster, does that mean that stuff falls in the direction in which the frequency of electromagnetic radiation is faster? ( I am thinking that atomic clocks measure time as a frequency which changes in proximity to mass relative to a distant observer). Therefore proximity to matter increases the frequency of electromagnetic radiation which produces the change in the rate of the flow of time as measured by an observer at a distance ?

### Re: Gravity

Posted: **December 7th, 2018, 8:58 pm**

by **Itsallaguess**

colin wrote:

I caught the tail end of a Jim Al-Khalili program on Gravity last night where he said that stuff seems to fall in the direction in which time flows faster, does that mean that stuff falls in the direction in which the frequency of electromagnetic radiation is faster? ( I am thinking that atomic clocks measure time as a frequency which changes in proximity to mass relative to a distant observer).

Therefore proximity to matter increases the frequency of electromagnetic radiation which produces the change in the rate of the flow of time as measured by an observer at a distance ?

I think the program is still available on BBC iPlayer for anyone that's interested -

https://www.bbc.co.uk/iplayer/episode/b ... -our-livesCheers,

Itsallaguess

### Re: Gravity

Posted: **December 7th, 2018, 9:36 pm**

by **XFool**

colin wrote:I caught the tail end of a Jim Al-Khalili program on Gravity last night where he said that stuff seems to fall in the direction in which time flows faster,

Actually, in which time flows

slower.

https://www.theguardian.com/books/2018/ ... lo-rovellicolin wrote:does that mean that stuff falls in the direction in which the frequency of electromagnetic radiation is faster? ( I am thinking that atomic clocks measure time as a frequency which changes in proximity to mass relative to a distant observer). Therefore proximity to matter increases the frequency of electromagnetic radiation which produces the change in the rate of the flow of time as measured by an observer at a distance ?

Allowing for the above mentioned reversal, the answer is yes. Clocks do run slower in a higher gravitational field (lower 'down') such as on the surface of the Earth rather than in orbit above it.

This is why the GPS clocks have to be adjusted as they run faster in orbit than on Earth. But then they also have to be compensated for running slower due to moving at high speed relative to people on the surface! In that case, overall, the gravity effect of the clock being high above the Earth wins out.

http://www.astronomy.ohio-state.edu/~po ... 5/gps.html

### Re: Gravity

Posted: **December 8th, 2018, 10:48 am**

by **colin**

Ah slower, thanks for correcting.

Must admit that I can mentally picture changes in the rate of flow of time far more easily if i see it as changes in the general frequency of electromagnetic radiation which underlie the rate at which all other processes proceed.

### Re: Gravity

Posted: **December 15th, 2018, 6:41 pm**

by **GrahamPlatt**

Just finished reading Carlo Rovelli's book "Reality is not what it seems". Subtitle The journey to quantum gravity. Sometimes a bit confusing to the layman (me), but it sparkles in places - especially the historical aspects. Well worth the effort. I feel a bit less ill-informed than before.

### Re: Gravity

Posted: **December 15th, 2018, 7:00 pm**

by **colin**

Subtitle The journey to quantum gravity.

Can that journey be summarized in a few sentences?

### Re: Gravity

Posted: **December 16th, 2018, 8:31 am**

by **jackdaww**

ive thought for a while that there is no such thing as time .

stuff is continuously changing thats all .

### Re: Gravity

Posted: **December 16th, 2018, 8:44 am**

by **Dod101**

I can recommend Carlo Rovelli's 'Reality is not what it seems' . His latest one, 'The Order of Time' I found very hard going in places. I conclude that whilst the layman ought to try to get a grip on these matters, fundamentally I do not think they are going to matter too much, to me at least. In fact I quite like 'Are you an Illusion?' by Mary Midgley, part of the 'heretics' series which gives an interesting counter to the theoretical physics of the likes of Rovelli. Sadly she died recently so there will be no more from her.

Rovelli is worth reading an a number of levels not least because it is a very approachable style which I imagine is in the original Italian and the translation has carried it forward very well.

Dod

### Re: Gravity

Posted: **December 16th, 2018, 1:43 pm**

by **Stonge**

+1 Reality is not What It Seems

Though theoretical physics is not mathematically understandable for everyone, the concepts (properly explained) certainly are.

### Re: Gravity

Posted: **December 16th, 2018, 4:03 pm**

by **colin**

ive thought for a while that there is no such thing as time .

stuff is continuously changing thats all .

Top

yes but the stuff all seems to change in the same direction as regards entropy and the same stuff appears to change at different rates depending on relative speed and proximity to mass.

Though theoretical physics is not mathematically understandable for everyone, the concepts (properly explained) certainly are.

Top

The problem for me is that different writers explain the same aspect of relativity in different ways that to me do seem to be mutually incompatible.

### Re: Gravity

Posted: **December 17th, 2018, 11:38 pm**

by **9873210**

Stonge wrote:+1 Reality is not What It Seems

Though theoretical physics is not mathematically understandable for everyone, the concepts (properly explained) certainly are.

Physicists, like mathematicians, are fundamentally lazy. They use mathematics because it is by far the easiest way to explain things. It might be possible to properly explain in some other way, but it would take far longer than just teaching the maths first.

Further if anybody does come up with an easier way the mathematicians will be all over it and it will become the new maths.

### Re: Gravity

Posted: **December 18th, 2018, 11:21 am**

by **colin**

Physicists, like mathematicians, are fundamentally lazy. They use mathematics because it is by far the easiest way to explain things. It might be possible to properly explain in some other way, but it would take far longer than just teaching the maths first.

I do not agree with this, Einstein thought up relativity theory through his 'thought experiments' which followed through the logical consequences of the speed of light being the same for all observers. The maths which he subsequently needed help to develop was necessary to produce the field equations necessary to test his theories in the real world.

### Re: Gravity

Posted: **December 18th, 2018, 11:31 am**

by **Stonge**

Science cannot explain, it can only describe.

### Re: Gravity

Posted: **December 18th, 2018, 11:39 am**

by **Dod101**

9873210 wrote:Physicists, like mathematicians, are fundamentally lazy. They use mathematics because it is by far the easiest way to explain things. It might be possible to properly explain in some other way, but it would take far longer than just teaching the maths first.

Further if anybody does come up with an easier way the mathematicians will be all over it and it will become the new maths.

I find the cynicism embodied in this sort of comment quite disturbing. I am not competent to judge whether the comment is true or not but when one looks at the work and thought that has gone into their subject by those such as Einstein and James Clerk Maxwell to name but two I rather doubt that laziness is one of their attributes.

Dod

### Re: Gravity

Posted: **December 18th, 2018, 2:09 pm**

by **colin**

It's just a silly comment, the equations necessary to use general relativity to make predictions are said to be among the hardest in physics, it takes years of study to be able to make sense of a few blackboards worth of scribbles.

### Re: Gravity

Posted: **December 18th, 2018, 10:49 pm**

by **9873210**

It is neither silly nor cynical. It is, perhaps, an in joke.

If you google "laziness as a virtue" you will find things like

this. While this refers to programmers the concept dates to before computer science was thrown out of the maths department.

It applies equally to physicists. (And probably dates to before physics was thrown out of the maths department.) They are looking for the simplest, easiest to use, explanation. If the maths is hard it means they don't know of an easier way to do it. But they are looking for an easier way and will use it if one is found.

If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is. -- John von Neumann

### Re: Gravity

Posted: **December 19th, 2018, 7:46 am**

by **Dod101**

This is I assume, is 9873210's way of showing his erudition. His quote is perfectly understandable, but I would prefer an exhortation to 'keep it simple' which most laymen (I assume that to be the majority on this Board) would understand.

Dod

### Re: Gravity

Posted: **December 19th, 2018, 5:13 pm**

by **colin**

I still believe that as a layman I can be taken a long way toward understanding gravity by being told that objects fall in the direction in which the frequency of electromagnetic radiation makes it easiest to fall, if we are simply told that the maths describing the changing frequencies matches the acceleration rate of objects falling toward the earth then for me at least the penny is falling too because at last I can see the underlying reason for gravity , though I don't understand why the mere presence of large amounts of matter should change these frequencies. The way it is usually presented to the uneducated public like me is that we are told that space is warped, but that just sends me down the path of wondering what is space made of which allows it to be warped? surly not a big 3d rubber sheet! Just another enigmatic conundrum. An ability to use the field equations is essential for using the theory to make predictions but surly not to understand some essential part of the underlying process which the equations describe?

### Re: Gravity

Posted: **December 19th, 2018, 9:15 pm**

by **XFool**

9873210 wrote:If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is. -- John von Neumann

It's all very well for him to say that.

### Re: Gravity

Posted: **December 19th, 2018, 10:07 pm**

by **stewamax**

Dod101 wrote:I can recommend Carlo Rovelli's 'Reality is not what it seems' . His latest one, 'The Order of Time' I found very hard going in places

Rovelli is a minority 'loop quantum gravity' man, and LQG's attempt to quantise space and time is still at variance with the smooth (non-quantised) space and time of Einsteinâ€™s theory of gravity. I have a copy of

The Order of Time and the disparity between the better known string theory (which - roughly - treats matter as vibrating strings

within 10-dimensional space-time) and LQG (which quantises the space-time itself) makes some of his arguments hard to comprehend. But that could be because I am thick!